The CSS data type applies to measurements for the following CSS properties: width, height, margin, padding, font-size, border-width, text-shadow, etc. There are two types of length units: relative and absolute.

Relative units

Font-relative lengths:

  1. em
  2. ex
  3. ch
  4. rem

Viewport-percentage length:

  1. vh
  2. vw
  3. vmin
  4. vmax

Relative to the font-size of the parent element. 3 em means 3 times the size of the font that has its parent.

Relative to the x-height of the current font.

Relative to width of the “0” (zero, the Unicode character U+0030) in the element’s font.

Relative to font-size of the root element (html).

em and rem units are used to create scalable layouts.


Viewport-percentage lengths defined a length relatively to the size of viewport, that is the visible portion of document.

Relative to 1% of the width of the viewport

Relative to 1% of the height of the viewport

Relative to 1% of viewport’s smaller dimension: between the height and the width of the viewport.

Relative to 1% of vieport’s larger dimension: between the height and the width of the viewport.

Absolute units

  • in – inches 1in = 2.54cm = 96px
  • cm – centimeters 1cm = 37.8px
  • mm – milimeters 1 mm = 0.1cm = 3.78px
  • pt – points – the points used by CSS are equal to 1/72nd of 1in.
  • pc – picas – 1pc = 12pt.
  • px – pixel – 1px = 0.75pt

Pixels have nothing to do with the screen pixels. Pixels (px) are relative to the viewing device: low-dpi devices or high resolution screens. Now we have CSS px which is a Angular Measurement.


Posted in CSS

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